toEqual() on Object with undefined values

[jcoyne]

🐛 Bug Report

When calling toEqual on an object, where one of the values is undefined does not compare that key.

To Reproduce

This assertion fails:

    expect({foo: 1, bar: undefined}).not.toEqual({foo: 1})

  ● toEqual › should compare objects

    expect(received).not.toEqual(expected)

    Expected value to not equal:
      {"foo": 1}
    Received:
      {"bar": undefined, "foo": 1}

      1 | describe('toEqual', () => {
      2 |   it('should compare objects', () => {
    > 3 |     expect({foo: 1, bar: undefined}).not.toEqual({foo: 1});
      4 |   });
      5 | });

Expected behavior

That should pass.

Link to repl or repo (highly encouraged)

https://repl.it/repls/KeenSnappyCodewarrior

Run npx envinfo --preset jest

Paste the results here:

$ npx envinfo --preset jest
npx: installed 1 in 1.377s

  System:
    OS: macOS 10.14.5
    CPU: (12) x64 Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz
  Binaries:
    Node: 11.7.0 - /usr/local/homebrew/bin/node
    Yarn: 1.13.0 - /usr/local/homebrew/bin/yarn
    npm: 6.9.0 - /usr/local/homebrew/bin/npm
  npmPackages:
    jest: ^24.7.1 => 24.7.1

[jeysal]

Use toStrictEqual for that. We'd like it to be the default, but that'd be a big breaking change

[jcoyne]

Thanks for the advice. I totally missed that in the docs. I wonder if this section should be updated to point people there: https://jestjs.io/docs/en/using-matchers#common-matchers

[jeysal]

Yes, I think it would be a good idea to suggest toStrictEqual in there. Do you want to send a PR? :)

[github-actions]

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